This is an examinable patent application under Section 111(a) submitted for a formal filing receipt.
1. Field of the Invention
The present invention lies in the field of helical bladed, rotors and their sealing assemblies on the drive end of the rotors serving as continuous mixers for plastic materials.
2. Background of the Invention
The present invention relates to the operating problems encountered with sealing arrangements for a rotatable shaft, like a helical rotor. During rotor turning, a sealing pressure is built up and maintained in the molten materials as enclosed within the annular clearances provided between the rotors and the surrounding barrel by means of the helical ridges moving within the mixer. The current practice for a drive end journal, or rotor pilot component, requires a packing gland seal means to effect a compression on the packing component itself, so that its seals against an outer wear sleeve. The currently accepted sealing means is effective for only a relatively short time. This occurs because the particulate feed materials, and in their thermoplastic forms, work their way into the seal assembly itself. This then serves to harden the packing component, eventually to the extent that it appreciably stiffens, and the packing will no longer seat tightly against the wear sleeve. The positive air pressure in the mixer will cause the leaking of particulates to flow through the impaired sealing means, creating mixer site contamination, impacting worker cleanliness, and risking operating safety.
Accordingly, it is a principal object of the invention to provide a visco sealing means in which particulate and molten materials do not bleed through the sealing means so as to generate site contamination.
It is another object to maintain the required sealing pressure at desired speeds of helical rotor rotation.
Yet another object of the invention is to eliminate any air pressure leakage from the mixing cylinder upon startup until the working area is loaded with molten material and/or particularly feed.
A still further object of the invention is to reduce seal area wear and packing seals degeneration so as to extend the operational range for a given sealing means assembly.
According to the invention, there is now provided a continuous mixer apparatus adapted for commingling of particulate thermoplastic materials of varying polymeric compositions, and having a mixer barrel, at least one main rotor with a helical profile body section at one end thereof, a driven journal located at the opposite end thereof, a drive end rotor plate, a drive end packing seal retainer, and a packing gland seal means, the improvement in the packing gland seal means which comprises: a bushing-like, visco sleeve assembly having a cylindrical inner surface being provided with an integral continuous, first peripheral annular ridge located proximal to the one longitudinal end of the sleeve assembly, which one end is distal from the helical profile body; a generally sleeve-shaped, metallic liner positioned adjacent the inner periphery ridge of the assembly; a sleeve-like, circular visco seal, being stepped-down intermediate the ends thereof, having first and second cylindrical peripheries, with the lesser diameter, periphery seal being located distal from the helical profile body section and with the larger diameter periphery seal being provided with a visco seal threading, and with the sleeve assembly and circular visco seal defining an annulus-type inner chamber there between; a single, rope-like first packing component positioned about the visco seal periphery and abutting the annular ridge of the sleeve subassembly; and the packing seal retainer being L-shaped and positioned adjacent the sleeve subassembly and also abutting and compressing laterally the first packing component.